The present invention relates to fabric conditioning compositions, and in particular, relates to concentrated cationic fabric softener compositions in the form of water-in-oil micro-emulsions.
Rinse added fabric conditioning compositions are well known. Typically, such compositions comprise a fabric softening agent dispersed in water. The fabric softening agent can be included at up to 8% by weight, in which case the compositions are considered dilute, or at levels from 8% to 60% by weight, in which case the compositions are considered concentrated.
In addition to softening, fabric conditioning compositions desirably have other properties, including stability upon storage, good dispersibility in water and delivery of sufficient amounts of perfume to the fabric being treated.
One of the problems frequently associated with conventional concentrated fabric conditioner compositions is physical instability upon storage. This problem is usually accentuated when the composition is stored at low temperature (e.g. at 5xc2x0 C. or below) or at elevated temperatures.
Physical instability can manifest itself as a thickening of the composition. This thickening can occur to a level at which the composition is no longer pourable, and, can even lead to the formation of an irreversible gel. Such thickening is very undesirable because the composition can thereafter no longer be conveniently used and/or it is unattractive to the consumer.
However, fabric conditioning concentrates are increasingly desired by the consumer. The consumer requires these products to be stable upon storage.
EP 0 829 531 Al (Unilever) discloses a concentrated fabric conditioner composition, comprising a cationic softener suspended in oil, which delivers perfume benefits to the fabric being treated.
Concentrated, clear compositions containing fabric softening actives have been disclosed in WO 98/08924 and WO 98/47991 (both Procter and Gamble). Such compositions comprise bio-degradable fabric conditioners. However, both disclose compositions comprising water miscible solvents which do not form water-in-oil micro-emulsions.
Clear fabric conditioning compositions have also been disclosed in EP 730023 (Colgate Palmolive), WO 96/19552 (Colgate Palmolive), WO 97/47723 (Colgate Palmolive), WO 96/33800 (Witco Co.), WO 97/03170 (Procter and Gamble), WO 97/03172 (Procter and Gamble), WO 97/03169 (Procter and Gamble), U.S. Pat. No. 5,492,636 (Quest Int.) and U.S. Pat. No. 5,427,697 (Procter and Gamble).
A further problem associated with many conventional concentrated fabric conditioners is that the perfume intensity in the composition decreases significantly during storage. This, correspondingly, results in a less xe2x80x98perfumedxe2x80x99 effect being given to fabric treated with the composition.
However, perfume longevity during storage and perfume delivery are also highly valued by the consumer. Therefore, it is desirable to provide a fabric treatment composition which gives increased perfume longevity during storage, and, better perfume delivery in use.
Thus, the present invention seeks to address one or more of the above-mentioned problems, and, to give one or more of the above-mentioned benefits desired by consumers.
Surprisingly, we have found that a fabric conditioning composition in the form of a micro-emulsion has good physical stability upon storage, increased perfume longevity and improved perfume delivery to the fabric. In addition, providing the composition as a micro-emulsion appears to improve both dispersion of the composition in water and dispensing of the composition from a dispensing drawer of a washing machine.
According to the present invention there is provided an aqueous fabric conditioning composition comprising:
(i) one or more cationic surfactants selected from:
(a) quaternary ammonium compounds having at least one ester group and being formed from a parent fatty acid having a degree of unsaturation represented by an iodine value of from 20 to 140 and,
(b) quaternary ammonium compounds having two C8-C28 alkyl or alkenyl chains directly attached to the nitrogen and being formed from a parent fatty acid having a degree of unsaturation represented by an iodine value of from 0 to 20 and,
(ii) one or more oils,
(iii) one or more solvents,
the composition being in the form of a micro-emulsion.
According to the invention, there is also provided a process for conditioning fabrics comprising the step of adding to a laundry operation the abovementioned fabric conditioning composition.
According to the invention, there is also provided a method for preparing an aqueous fabric conditioning composition comprising mixing a cationic surfactant, an oil, a solvent and water and either agitating or heating the mixture to form a micro-emulsion.
According to the invention, there is further provided a macro-emulsion formed by diluting the aforementioned fabric conditioning composition with water.
The present invention is particularly concerned with cationic fabric softening compositions which are in the form of water-in-oil micro-emulsions.
In the context of the present invention, the term xe2x80x98micro-emulsionxe2x80x99 means a liquid product which is clear or translucent, isotropic and thermodynamically stable over a specified temperature range. It does not include conventional macro-emulsions which are not clear and isotropic.
The compositions of the invention are typically thermodynamically stable above 10xc2x0 C. Below 10xc2x0 C. the compositions may become hazy but recover upon warming to ambient temperature where they revert back to a clear isotropic micro-emulsion. When diluted, the compositions are transformed to inverse macro-emulsions (including multiple emulsions) which typically have droplet sizes of 10 xcexcm or less or mesophases.
Without wishing to be bound by theory, it is believed that the compositions of the invention have a physical state wherein water droplets are stabilised within an oil continuous phase by the cationic surfactant and, if present, a dispersibility aid. Typically, the water droplets in the emulsion have a diameter of between 50-500 xc3x85. The physical structure can be bicontinuous in nature (for an explanation of the physical structures see Micelles, Membranes, Micro-emulsions and Mono-layers, Ed. Gelbart et. al., Springler-Verlag, Chapter 7).
The fabric conditioning composition of the present invention comprises one or more cationic surfactants.
These surfactants are fabric softening compounds which are typically included in rinse-added fabric softening compositions.
The surfactants may be quaternary ammonium compounds having at least one ester group and being formed from a parent fatty acid having a degree of unsaturation represented by an iodine value of from 20 to 140 (referred to as type (a) herein).
Alternatively, the cationic surfactants may comprise quaternary ammonium compounds having two C8-C28 alkyl or alkenyl chains being directly attached to the nitrogen with the compound being formed from a parent fatty acid having a degree of unsaturation represented by an iodine value of from 0 to 20 (referred to as type (b) herein).
Preferably, the average chain length of the alkyl or alkenyl group is at least C14, more preferably at least C16. Most preferably at least half of the chains have a length of C18.
Mixtures of the aforementioned types of cationic surfactants, that is mixtures of either type (a) or (b), may also be used according to the invention.
It is generally preferred if the alkyl or alkenyl chains are predominantly linear.
It is especially preferred if the cationic surfactant is a water insoluble quaternary ammonium material which comprises a compound having two C12-18 alkyl or alkenyl groups connected to the nitrogen head group via at least one ester link. It is more preferred if the quaternary ammonium material has two ester links present.
A first group of preferred ester-linked cationic surfactant materials for use in the invention is represented by formula (I): 
wherein each R1 group is independently selected from C1-4 alkyl, hydroxyalkyl or C2-4 alkenyl groups; and wherein each R2 group is independently selected from C8-28 alkyl or alkenyl groups; 
Xxe2x80x3 is any anion compatible with the cationic surfactant, such as halides or alkyl sulphates, e.g. chloride, methyl sulphate or ethyl sulphate and n is 0 or an integer from 1-5.
These compounds are type (a) compounds as herein defined.
Especially preferred materials within this formula are di-alkenyl esters of triethanol ammonium methyl sulphate and N-N-di(tallowoyloxy ethyl) N,N-dimethyl ammonium chloride. Commercial examples of compounds within this formula are Tetranyl(copyright) AOT-1 (di-oleic ester of triethanol ammonium methyl sulphate 80% active), AO-1 (di-oleic ester of triethanol ammonium methyl sulphate 90% active), L1/90 (partially hardened tallow ester of triethanol ammonium methyl sulphate 90% active), L5/90 (palm ester of triethanol ammonium methyl sulphate 90% active (supplied by Kao corporation) and Rewoquat WE15 (C10-C20 and C16-C18 unsaturated fatty acid reaction products with triethanolamine dimethyl sulphate quaternised 90% active), ex Witco Corporation.
A second preferred type of quaternary ammonium material is represented by formula (II): 
wherein R1, R2, n and Xxe2x88x92 are as defined above.
These compounds are also type (a) cationic surfactants as herein defined.
Preferred materials of this class such as 1,2bis[tallowoyloxy]-3-trimethylammonium propane chloride and 1,2-bis[oleyloxy]-3-trimethylammonium propane chloride and their method of preparation are, for example, described in U.S. Pat. No. 4,137,180 (Lever Brothers), the contents of which are incorporated herein. Preferably these materials also comprise small amounts of the corresponding monoester, as described in U.S. Pat. No. 4,137,180.
For type (a) cationic surfactants, the total average iodine value of the parent fatty acid from which R1 is formed is from 20 to 140, more preferably from about 50 to 130, most preferably from about 80 to 100.
A third preferred type of quaternary ammonium material is represented by formula (III): 
where R1 and R2 are C8-28 alkyl or alkenyl groups; R3 and R4 are C1-4 alkyl or C2-4 alkenyl groups and Xxe2x88x92 is as defined above.
Examples of compounds within this formula include di(tallow alkyl)dimethyl ammonium chloride, di(tallow alkyl) dimethyl ammonium methyl sulphate, dihexadecyl dimethyl ammonium chloride, di(hardened tallow alkyl) dimethyl ammonium chloride, dioctadecyl dimethyl ammonium chloride and di(coconut alkyl) dimethyl ammonium chloride.
These compounds are type (b) cationic surfactants as herein defined.
For type (b) cationic surfactants, the total average iodine value of the parent fatty acid from which R1 to R4 inclusive are formed is from 0 to 20, more preferably from 0 to 10, most preferably from 0 to 5.
It is advantageous for environmental reasons if the quaternary ammonium material is biologically degradable.
Preferably, the compositions are provided as concentrates comprising from 10-60% by weight of cationic surfactant (active ingredient) based on the total weight of the composition, more preferably 20-55% by weight, most preferably 24-51% by weight.
Compositions comprising less than 10% by weight of cationic surfactant can be provided, but this is less desirable as higher levels of oil are required in the composition.
Preferred cationic surfactant compounds are substantially water insoluble.
xe2x80x98Substantially water insolublexe2x80x99 surfactant compounds in the context of this invention are defined as compounds having a solubility less than 1xc3x9710xe2x88x923 wt % in demineralised water at 20xc2x0 C. Preferably the cationic surfactants have a solubility less than 1xc3x9710xe2x88x924. Most preferably the cationic surfactants have a solubility at 20xc2x0 C. in demineralised water from 1xc3x9710xe2x88x928 to 1xc3x9710xe2x88x926 wt %.
In the context of the present invention, iodine value of the parent fatty acid of the cationic surfactant is defined as the number of grams of iodine which react with 100 grams of compound.
To calculate the iodine value of a parent fatty acid of a cationic surfactant, a prescribed amount (from C.1-3 g) of the fatty acid was dissolved into about 15 ml chloroform. The dissolved parent fatty acid was then reacted with 25 ml of iodine monochloride in acetic acid solution (0.1 M). To this, 20 ml of 10% potassium iodide solution and about 150 ml deionised water was added. After addition of the halogen to the parent fatty acid had taken place, the excess of iodine monochloride was determined by titration with sodium thiosulphate solution (0.1 M) in the presence of a blue starch indicator powder. At the same time a blank was determined with the same quantity of reagents and under the same conditions. The difference between the volume of sodium thiosulphate used in the blank and that used in the reaction with the parent fatty acid enabled the iodine value to be calculated.
The compositions of the present invention comprise at least one oil. The oil may be a mineral oil, an ester oil and/or natural oils such as vegetable oils. However, ester oils or mineral oils are preferred.
The ester oils are preferably hydrophobic in nature. They include fatty esters of mono or polyhydric alcohols having from 1 to 24 carbon atoms in the hydrocarbon chain, and mono or polycarboxylic acids having from 1 to 24 carbon atoms in the hydrocarbon chain, provided that the total number of carbon atoms in the ester oil is equal to or greater than 16, and that at least one of the hydrocarbon chains has 12 or more carbon atoms.
Suitable ester oils include saturated ester oils, such as the PRIOLUBES (ex. Unichema). 2-ethyl hexyl stearate (PRIOLUBE 1545), neopentyl glycol monomerate (PRIOLUBE 2045) and methyl laurate (PRIOLUBE 1415) are particularly preferred although oleic monoglyceride (PRIOLUBE 1407) and neopentyl glycol dioleate (PRIOLUBE 1446) are also suitable.
It is preferred that the viscosity of the ester oil is from 0.002 to 0.4 Pa.S (2 to 400 cps) at a temperature of 25xc2x0 C. at 106sxe2x88x921, measured using a Haake rotoviscometer, and that the density of the mineral oil is from 0.8 to 0.9 g.cmxe2x88x923 at 25xc2x0 C.
Suitable mineral oils include branched or straight chain hydrocarbons (e.g. paraffins) having 8 to 35, more preferably 9 to 20 carbon atoms in the hydrocarbon chain.
Preferred mineral oils include the Marcol technical range of oils (ex Esso) although particularly preferred is the Sirius range (ex Silkolene) or Semtol (ex. Witco Corp.). The molecular weight of the mineral oil is typically within the range 100 to 400.
One or more oils of any of the above mentioned types may be used.
It is believed that the oil provides excellent perfume delivery to the cloth and also increases perfume longevity upon storage of the composition.
The oil may be present in an amount from 11-70% by weight, more preferably 12-60%, by weight most preferably 15-52%, e.g. 20-45% by weight based on the total weight of the composition.
Preferably, the weight ratio of cationic softener to oil in the composition is in the range 5:1 to 1:10, more preferably 4:1 to 1:5, most preferably 3:1 to 1:3.
The oil referred to herein, is preferably added to the composition as a separate component, that is, in addition to any oil which may be present in other components of the composition.
The compositions also comprise one or more solvents. The solvent is preferably organic, such as a low molecular weight (preferably 180 or less) alcohol, including monohydric and polyhydric alcohols, e.g. diols.
The presence of the lower molecular weight alcohol helps improve physical stability upon storage by lowering the viscosity to a more desired level and also assists the formation of the micro-emulsion. Examples of suitable alcohols include ethanol, isopropanol, n-propanol, dipropylene glycol, t-butyl alcohol, hexylene glycol, and glycerol.
The solvent may be added to the composition either by being present as a component in the cationic surfactant or it may be added separately.
The solvent is preferably present in an amount from 0.05% to 40% by weight, more preferably from 0.1% to 25% by weight, most preferably from 0.15% to 16% by weight, based on the total weight of the composition.
Preferably the weight ratio of cationic softener to solvent in the composition is in the range 8:1 to 1:3, more preferably 6:1 to 1:2, most preferably 4:1 to 1:1.
Mixtures of solvents may be used if desired.
The compositions of the invention are aqueous based.
Typically, the level of water present is from 0.5-35% by weight, more preferably 1-29% by weight, even more preferably 2-27% by weight, most preferably 3-25% by weight, based on the total weight of the composition.
Optionally and advantageously, the compositions contain one or more dispersion aids. The dispersion aid assists the dispersion of the micro-emulsion when it is diluted in water.
Especially preferred dispersion aids for use in the compositions of the invention are alkoxylated nonionic fatty alcohols, such as C10-C22 alkyl/alkenyl alkoxylated with 3-20 moles alkoxy moieties. The fatty alcohols may be alkoxylated with ethylene oxide, propylene oxide or ethylene oxide/propylene oxide mixtures.
Other dispersion aids which may be used in the compositions of the invention can be selected from mono-long chain alkyl cationic quaternary ammonium compounds and mono-long chain alkyl amine oxides.
Preferably the concentration of the dispersion aid is from 0.05-30% by weight, more preferably from 0.3-20% by weight, most preferably from 1-15% by weight, based on the total weight of the composition.
The dispersion aid may also act as a stabiliser for the micro-emulsion so that addition of the dispersion aid provides a more stable micro-emulsion product.
It is particularly preferred that a dispersion aid is present when, in compositions containing type (a) cationic surfactant compounds as herein defined, at least 10% by weight of water is present or, in compositions containing type (b) cationic surfactant compounds as herein defined, at least 3% by weight of water is present, based on the total weight of the composition.
The weight ratio of the quaternary cationic softening compound to the total amount of dispersion aid is from 3:1 to 8:1, more preferably 5:1 to 7:1.
The compositions of the invention may, optionally, comprise one or more additional stabilisers which stabilise against oxidation and/or reduction.
If the stabilisers are present as anti-oxidants, they may be added at a level of from 0.005 to 2% by weight based on the total weight of the composition, more preferably from 0.01 to 0.2% by weight, most preferably from 0.035% to 0.1% by weight.
If present as an anti-reduction agent then the stabiliser is preferably used in an amount from 0.001% to 0.2% by weight based on the total weight of the composition.
The stabilisers assist by assuring good odour stability upon storage particularly when the composition is prepared using a surfactant having substantial unsaturated character (i.e. type (a) surfactants as herein defined).
Typically, such additional stabilisers include mixtures of ascorbic acid, ascorbic palmitate and propyl gallate (under the tradenames Tenox(copyright) PG and Tenox(copyright) S-1); mixtures of butylated hydroxytoluene, butylated hydroxyanisole, propyl gallate and citric acid (under the tradename Tenox(copyright) 6); tertiary butylhydroquinone (under the tradename Tenox(copyright) TBHQ); natural tocopherols (under the tradenames Tenox(copyright) GT-1 and GT-2); long chain esters of gallic acid (under the tradenames Irganox(copyright) 1010, Irganox(copyright) 1035, Irganox(copyright) B 117 and Irganox(copyright) 1425) and mixtures thereof. Tenox products are supplied by Eastman Chemical Products Inc. Irganox products are supplied by Eastman Chemical Products Inc. The above stabilisers can also be mixed with chelating agents such as citric acid; 1-hydroxyethylidene-1,1-diphosphonic acid (Dequest(copyright) 2010, ex Monsanto); 4,5-dihydroxy-m-benzene-sulphonic acid/sodium salt (under the tradename Tiron(copyright), ex Kodak) and diethylenetriaminepentaacetic acid (under the tradename DTPA(copyright), ex Aldrich).
Co-active softening surfactants for the cationic surfactant may also be incorporated in an amount from 0.01 to 20% by weight, more preferably 0.05 to 10%, based on the total weight of the composition. Preferred co-active softening surfactants are fatty acids, fatty amines and fatty N-oxides.
The compositions of the invention may also comprise one or more perfumes.
When present, the perfume is used in a concentration of preferably from 0.01-15% by weight, more preferably from 0.05-10% by weight, most preferably from 0.1-5% by weight, e.g. 0.15 to 4.5% by weight based on the total weight of the composition.
The compositions may also contain one or more optional ingredients conventionally included in fabric conditioning compositions such as pH buffering agents, perfume carriers, fluorescers, colourants, hydrotropes, antifoaming agents, antiredeposition agents, polyelectrolytes, enzymes, optical brightening agents, anti-shrinking agents, anti-wrinkle agents, anti-spotting agents, germicides, fungicides, anti-corrosion agents, drape imparting agents, anti-static agents, ironing aids and dyes.
The compositions of the invention may be prepared according to any suitable method.
In a first method, a mixture of an oil, a low molecular weight solvent, a dispersibility aid, water and a cationic surfactant are stirred under low agitation until a clear composition is formed having a viscosity of 0.5 Pa.S (500 cps) or less at a shear rate of 106sxe2x88x921 at 25xc2x0 C., measured using a Haake rotoviscometer.
In a second method a mixture of an oil, a low molecular weight solvent, a dispersibility aid, water and a cationic surfactant are heated until a molten mixture is formed and then the mixture is left to cool. Perfume is added to the mixture when it reaches ambient temperature.
The micro-emulsion is easily obtained with only gentle agitation of the composition ingredients (in the first method) or a small thermal activation (in the second method) being required to accelerate micro-emulsification.
In its undiluted state at ambient temperature the product is in the form of a micro-emulsion, preferably a water-in-oil micro-emulsion.
Preferably the compositions form stable micro-emulsions at between about 10xc2x0 C. and about 50xc2x0 C.
The compositions are generally provided in a highly concentrated form but have a viscosity that is acceptable to the consumer. Typically the compositions have a viscosity of 0.5 Pa.S (500 cps) or less, preferably 0.2 Pa.S (200 cps) or less, most preferably 0.12 Pa.S (120 cps) or less at a shear rate of 106sxe2x88x921 at 25xc2x0 C., measured using a Haake rotoviscometer.
The micro-emulsion compositions of the invention provide excellent storage stability across a wide temperature range. In the context of the present invention, the phrase xe2x80x98storage stabilityxe2x80x99 means that the liquid composition, which may solidify at low temperature, will revert to a stable micro-emulsion when the temperature is raised to about 10xc2x0 C. or above.
The composition is preferably used in the rinse cycle of a home textile laundering operation, where, it may be added directly in an undiluted state to the washing machine, e.g. through a dispenser drawer. Alternatively, it can be diluted prior to use. The compositions may also be used in a domestic hand-washing laundry operation.
When the composition is used in a diluted form, at least some of the composition formed comprises an oil in water macro-emulsion which typically has a viscosity of between 0.005-0.12 Pa.S (5-120 cps), preferably at least 0.015 Pa.S (15 cps) at a dilution ratio of 1:9 (one part composition to 9 parts water) at a shear rate of 106sxe2x88x921 at 25xc2x0 C., measured using a Haake rotoviscometer.
When the composition is dispersed in water, the solution preferably has a pH of from 1.5 to 5.